Process of maing naphthacene from propargyl alcohol

ABSTRACT

A process for synthesizing a single isomer of a naphthacene compound comprises the steps of:
         (a) reacting a symmetrically substituted 1,1-diarylpropargyl alcohol compound with a reagent capable of forming a leaving group to form a reaction mixture containing a intermediate; and then   (b) heating the intermediate in the presence of a solvent and in the absence of any oxidizing agent to form a single naphthacene compound.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is one of three applications cofiled under U.S.application Ser. Nos. 10/899,825, 10/899,919 , 10/899,821.

FIELD OF THE INVENTION

This invention relates to the synthesis of naphthacene compounds bearingat least two aryl groups using a symmetrically substituted benzophenoneand a mono-substituted acetylene compounds to form symmetricallysubstituted 1,1-diarylpropargyl alcohols, which are further reacted togive a single naphthacene compound.

BACKGROUND OF THE INVENTION

Organic electroluminescent (EL) devices have been known for over twodecades, their performance limitations have represented a barrier tomany desirable applications. In simplest form, an organic EL device iscomprised of an anode for hole injection, a cathode for electroninjection, and an organic medium sandwiched between these electrodes tosupport charge recombination that yields emission of light. Thesedevices are also commonly referred to as organic light-emitting diodes,or OLEDs.

The organic layers in these devices are usually composed of a polycyclicaromatic hydrocarbon. Substituted naphthacenes is one class offluorescent materials useful in the manufacture of EL devices. Thenaphthacene known as rubrene, or 5,6,11,12-tetraphenylnaphthacene, iscommercially available and can be prepared by reacting1,1,3-triphenylpropargyl alcohol with thionyl chloride and heating theresulting product in the presence of an organic hindered amine base.However, the yields of rubrene prepared in this manner are usually low,not reproducible and contain impurities. Rubrene, prepared in thismanner, must be subjected to extensive purification techniques to renderit sufficiently pure to be useful in EL devices. In addition, whensubstituents are present in the starting propargyl alcohol, formation ofnaphthacene isomers occurs.

Because rubrene and its derivatives are very prone to photo-oxidation,the normal purification techniques of re-crystallization andchromatography are not easily applied to the purification of the crudematerial from the reaction. Precautions have to be taken to eliminatethe presence of oxygen or light. Impurities and isomers from thepreparation procedure, and also the photo-oxidation products orendoperoxides as they are known, that contaminate rubrene or othernaphthacene derivatives give rise to EL devices with unacceptableperformance. Even very small amounts of impurities, such as 1% or less,can cause significant problems in EL devices.

Moureu et al., C.R. Acad. Sci. (1926), Vol. 182, 1440; Moureu et al.,Bull. de la Soc. Chim. de Fr. (1930), Vol. 47, 216; Wittig et al., J.Fur Praktische Chemie, (1942), Vol. 160, 242; Rigaudy et al.,Tetrahedron (1977), Vol. 33, 767; and Essenfeld, U.S. Pat. No. 4,855,520refer to the preparation of rubrene in yields ranging from 20-50% andemploy different techniques to purify the material.

Moureu et al., in C.R. Acad. Sci. (1926), Vol. 182, p. 1441, describesthe preparation of rubrene from 3-chloro-1,3,3-triphenylpropyne byheating this material from 71° C. to 120° C. in the absence of solvent.The purification and removal of impurities from the crude materialrequires an involved procedure of treating with different solvents.

Moureu et al., Bull. de la Soc. Chim. de Fr. (1930), Vol. 47, p. 217-220does not describes the preparation of rubrene but describes theinfluence of factors such as dilution and catalysts on the formationfrom 3-chloro-1,3,3-triphenylpropyne. The conclusion is that the bestprocedure for the preparation of rubrene from3-chloro-1,3,3-triphenylpropyne is by heating the material in theabsence of solvent. The purification and removal of impurities from thecrude material requires a very involved procedure of treating withdifferent solvents including the high boiling solvent, naphthalene.

Wittig et al., J. Fur Praktische Chemie, (1942), Vol. 160, p. 244 alsodescribes the preparation of rubrene from3-chloro-1,3,3-triphenylpropyne by heating this material under vacuum to120° C. in the absence of solvent. Again, the purification and removalof impurities from the crude material requires an involved procedure oftreating with different solvents.

Rigaudy et al., Tetrahedron (1977), Vol. 33, p. 773, describes thepreparation of rubrene from a cyclobutane derivative.

Essenfeld, in U.S. Pat. No. 4,855,520 describes a long and involvedprocedure for the preparation of naphthacenes in the presence of ahindered amine base, and reports a yield of 37%. The procedure calls forthe use of several different solvents. Careful removal of the initiallow boiling solvent from the reaction mixture is followed by the carefuladdition of a second solvent with a high boiling point. Hindered aminebases are disadvantageous in manufacturing processes because they areoftentimes expensive and not environmentally safe, requiring specialhandling and disposal procedures. Furthermore, when substituents areintroduced into the procedure of that described by Essenfeld,naphthacene isomers are formed. Isomer formation is undesirable inmaterials to be employed in EL devices because each isomer will havedifferent chemical and physical properties and would have to beseparated into single components before they could be used in the ELdevices. Separation into single isomers or components requiresadditional effort and is often difficult.

The stability and luminance performance of these fluorescent materialsin EL devices in general, tends to improve when fabricated from singlematerials with high purity. There is a continuing need in the ELindustry for new, short, environmentally friendly and simple proceduresfor the preparation of single isomer, high purity naphthacenes. Devicesfabricated from naphthacenes with low purity give poorer performing ELdevices and limit the applications of these EL devices.

The problem to be solved therefore is to provide a simple procedure thatwould yield high purity single naphthacene compounds. Such proceduresshould require minimum exposure to light and oxygen and which could beapplied to the preparation of naphthacenes with a variety ofsubstituents.

SUMMARY OF THE INVENTION

The invention provides a process for synthesizing a single isomer of anaphthacene compound comprising the steps of:

-   -   (a) reacting a symmetrically substituted 1,1-diarylpropargyl        alcohol compound with a reagent capable of forming a leaving        group to form a reaction mixture containing a intermediate; and        then    -   (b) heating the intermediate in the presence of a solvent and in        the absence of any oxidizing agent to form a single naphthacene        compound.

The process provides a simple and rapid way to prepare single isomers ofnaphthacene derivatives in good yield with high purity useful for OLEDdevices.

DETAILED DESCRIPTION OF THE INVENTION

The process of the invention is generally as described above. It is aprocess for synthesizing single isomers of symmetrically substitutednaphthacene compounds containing at least two aryl groups comprising astep (a), employing a symmetrically substituted 1,1-diarylpropargylalcohol and converting the alcohol group of said symmetricallysubstituted 1,1-diarylpropargyl alcohol into a leaving group to give aintermediate and step (b), further reacting said intermediate with theleaving group under heating conditions in the absence of either light oroxygen and in the presence of a solvent, into a single symmetricallysubstituted naphthacene compound.

The type, number and location of substituent groups on theaforementioned 1,1-diarylpropargyl alcohol is key to the currentinvention. The term symmetrically substituted is used to indicate thatthe type of substituent group as well as the number of substituents andtheir location, are identical on both the aryl groups of said1,1-diarylpropargyl alcohol. If the substituents on either of the arylgroups of the 1,1-diarylpropargyl alcohol are different, as in U.S. Pat.No. 4,855,520, then several isomers of the naphthacene compound areformed.

Optionally, an acid scavenger can be employed in step (a) of theinvention and can be an amine base or an inorganic base. The acidscavenger employed may be any material, which is known to be useful forthis purpose. Suitable scavengers useful in step (a) are primary,secondary or tertiary amine bases. Particularly useful amine bases aretriethylamine, pyridine, 1,8-diazobicyclo[5,4,0]undeca-7-ene,diisopropylethylamine, tetramethylethylenediamine and the like. Inaddition to amine bases, other useful acid scavengers are inorganicbases, such as the basic salts of metals or non-metals and inparticular, the basic salts of groups 1 and 2 of the periodic table.Specifically, metal and non-metal carbonates are other examples ofuseful inorganic scavengers. Examples of these inorganic bases useful inthe invention are Li₂CO₃, Na₂CO₃, K₂CO₃, Rb₂CO₃, Cs₂CO₃, MgCO₃, CaCO₃,BaCO₃, NaOAc also known as sodium acetate, and (NH₄)₂CO₃ also known asammonium carbonate, and the like but are not limited to these examples.

Optionally, a base can be employed in step (b) of the invention and canbe any amine or inorganic base. Useful amine bases include primary,secondary or tertiary amines including hindered amine bases.Particularly useful amine bases are triethylamine, pyridine,1,8-diazobicyclo[5,4,0]undeca-7-ene, diisopropylethylamine,tetramethylethylenediamine, collidine and lutidine bases and other likeorganic bases. Inorganic bases useful in step (b) of the invention arebasic salts of metals and non-metals. In particular, the basic salts ofgroups 1 and 2 of the periodic table. Specifically, metal and non-metalcarbonates are other examples of useful inorganic bases. Examples ofthese inorganic bases useful in step (b) of the invention are Li₂CO₃,Na₂CO₃, K₂CO₃, Rb₂CO₃, Cs₂CO₃, MgCO₃, CaCO₃, BaCO₃, NaOAc also known assodium acetate, and (NH₄)₂CO₃ also known as ammonium carbonate and thelike, but are not limited to these examples.

The solvents employed in steps (a) and (b) may be the same, or differentfor each step. Useful solvents for step (a) are diethyl ether, methylenechloride, tetrahydrofuran, ethyl acetate and the like. Particularlyuseful solvents for step (a) are solvents with low boiling points, whichcan be easily removed if they are to be replaced by a second solvent instep (b). Useful solvents for step (b) are benzene, toluene, xylene andxylene mixtures. Particularly useful solvents for step (b) are solventswith high boiling points, which are needed for the high temperaturesnecessary to get the reaction of step (b) to proceed at a reasonablerate. Alternatively, the high boiling point solvent described above forstep (b) can be employed in both steps (a) and (b) eliminating the needto replace the low boiling point solvent of step (a).

Temperatures useful in steps (a) and (b) are any temperatures suitableto bring about first, the reaction of step (a) and then the secondreaction of step (b). When the reagent capable of forming the leavinggroup in step (a) is reactive, the temperature for reaction to occur isnormally low and usually falls in the range of from −30° C. to +30° C.but is not limited to this range. A particularly useful temperaturerange for step (a) is from 0° C. to +20° C.

The temperature range required for step (b) is from +30° C. to +180° C.but is not limited to this range. A particularly useful temperaturerange for step (b) is from +70° C. to +120° C.

To prevent photo-oxidation of the naphthacene compound the reaction isconducted under either an inert atmosphere or in the absence of light.Most conveniently, both oxygen and light are excluded from the reaction.Oxygen present in air is considered an oxidizing agent when the reactionis exposed to light which causes photo-oxidation. To preventphoto-oxidation, an atmosphere of nitrogen is most conveniently employedin both steps (a) and (b).

The reaction time for step (a) is from 5 minutes to 3 hours but mostconveniently from 10 minutes to 30 minutes, while the reaction time forstep (b) is from 1 to 48 hours, but most conveniently complete in 1 to 8hours and usually in 4 to 5 hours.

The reagents used in the present invention to form the leaving group Xof the propargyl alcohol in step (a), can be any reagent used to formleaving groups with alcohols, particularly propargyl alcohols. Thehydrogen of the alcohol can be replaced to give oxygen based leavinggroups or the complete hydroxyl group can be replaced. When the completehydroxyl group is replaced, reagents such as thionyl chloride, thionylbromide, phosphorous trichloride, phosphorous tribromide, phosphorouspentachloride and phosphorous oxychloride may be selected, but is notlimited to this list. In these cases, the X group is Cl or Br. When justthe hydrogen of the propagyl alcohol is replaced, reagents such asalkanesulfonyl halides, acyl halides and anhydrides are useful reagentsbut are not limited to this list. Particularly useful reagents aremethanesulfonyl chloride and acetyl chloride. When methanesulfonylchloride is the reagent, the leaving group is methanesulfonate and isrepresented as CH₃SO₃, whereas the leaving group is acetate, representedby OAc, when the reagent is acetic anhydride or acetyl chloride.

The intermediate of step (a) can be represented by the symmetricallysubstituted Formulae (Ia) or (Ib) as follows:

wherein:

-   -   the R^(a) groups are selected from hydrogen or substituent        groups;    -   R^(b) is hydrogen or a substituent group;    -   n is selected from 0-4;    -   X is a leaving group; and        provided that when n is 0 Rb is not phenyl.

When the R^(b) group of Formulae (Ia) and (Ib) is a heterocyclic orcarbocyclic ring group then the intermediate of step (a) can berepresented by Formulae (IIa) and (IIb) as follows:

wherein:

-   -   the R^(a) and R^(c) groups are selected from hydrogen or        substituent groups;    -   n is selected from 0-4;    -   m is selected from 0-5;    -   W represents the atoms necessary to complete a heterocyclic or        carbocyclic ring group;    -   X is a leaving group; and        provided that when W forms a phenyl group the R^(a) and R^(c)        are not all hydrogen.

When the R^(b) group of Formulae (Ia) and (Ib) is an aryl group then theintermediate of step (a) can be represented by Formulae (IIIa) and(IIIb) as follows:

wherein:

-   -   the R^(a) groups are selected from hydrogen or substituent        groups;    -   R^(c) is hydrogen or a substituent group;    -   n is selected from 0-4;    -   m is selected from 0-5;    -   X is a leaving group; and        provided that R^(a) and R^(c) are not all hydrogen.

The intermediate of step (a) can be represented by either the acetylenesof Formulae (Ia), (IIa) and (IIIa) or by the allenes of Formulae (Ib),(IIb) and (IIIb). It is believed that the reagent used to form theleaving group first reacts with the propargyl alcohol of step (a) toinitially form the intermediates of Formulae (Ia) or (IIa) which thenrearrange to the allenes of Formulae (Ib) or (IIb). During the heatingin step (b) two of these allene molecules then react to form thenaphthacenes. On one occasion, this has been confirmed by isolating theintermediate of step (a) and carrying out a single crystal x-rayanalysis of the intermediate to determine its structure. When thisallene material is heated in a high boiling point solvent, thenaphthacene forms.

When the intermediate derivative of step (a) of the invention isrepresented by Formulae (Ia) or (Ib) then the naphthacenes of step (b)can be represented by Formulae (IVa) as follows:

When R^(b) in Formulae (Ia) or (Ib) represent a heterocyclic orcarbocyclic ring group then the naphthacenes of step (b) of theinvention can be represented by Formulae (IVb):

When W in Formulae (IIa) or (IIb) represent the atoms necessary tocomplete an aryl group the naphthacenes in step (b) of the invention canbe represented by Formulae (IVc):

The substituted 1,1-diarylpropargyl alcohol materials employed in step(a) of the invention are represented by Formulae (Va), (Vb) or (Vc) asfollows:

The term symmetrically substituted is used to indicate that the type ofsubstituent group R^(a), as well as the number n of R^(a) groups andtheir location, are identical on both the phenyl groups bearing thesegroups in Formulae (Ia), (IIa), (IIIa), (Ib), (IIb) and (IIIc). In theinvention, the R^(c) groups may or may not be identical to R^(a) interms of substituent type, number n, and location. When the R^(a) groupsare identical, only a single naphthacene isomer is formed.

The propargyl alcohols are readily available by the addition of theanion of a mono-substituted acetylene such as a mono-arylacetylene, to asymmetrically substituted benzophenone. The anion of themono-substituted acetylene can be prepared by the action of a strongbase, such as potassium tert-butoxide, with the mono-substitutedacetylene in an inert solvent such as dimethylformamide. Theaforementioned benzophenone and acetylene can be suitably substituted togive various symmetrically substituted propargyl alcohols.

The R, R^(a) and R^(b) groups of the current invention can be selectedfrom cyano, nitro, halogen, hydroxy, alkyl, alkenyl, alkoxy, aryl,aryloxy, acyl, oxysulfonyl, acyloxy, oxycarbonyl, carboxy, carbocyclic,heterocyclic, sulfoxide, thio, sulfamoyl, sulfonamido, sulfonyl,carbamoyl, carbonamido, ureido, and trifluoromethyl groups. Preferredcompounds of the invention are obtained when R is an aryl group, andR^(a) and R^(b) selected from aryl or alkyl groups. The numerical valueof n can be 0-4, but a preferred range is 0-3. The numerical value for mis 0-5, but a preferred range is 0-3. Particularly useful in theinvention is when n is 1 and m is 0-3 and the substituents areindividually located in the meta and para positions.

When R^(a) and R^(b) each constitute a ring, the rings can beindividually carbocyclic and heterocyclic in nature. When the ring iscarbocyclic a preferred ring is phenylene, which in combination with thephenyl groups in formulae (Ia)-(IVa) and (Ib)-(IVb) give a naphthalenegroup. Also, when R^(a) or R^(b) each form a heteroocyclic group thepreferred heterocyclic group is furyl, imidazolyl, pyrazolyl, pyridyl,pyrrolyl, thienyl, or triazolyl.

Unless otherwise specifically stated, use of the term “substituted” or“substituent” means any group or atom other than hydrogen. Additionally,when the term “group” or “compound” is used, it means that when a groupcontains a substitutable hydrogen, it is also intended to encompass notonly the group's unsubstituted form, but also its form furthersubstituted with any substituent group or groups as herein mentioned, solong as the substituent does not destroy properties necessary for deviceutility. Suitably, a substituent group may be halogen or may be bondedto the remainder of the molecule by an atom of carbon, silicon, oxygen,nitrogen, phosphorous, sulfur, selenium, or boron. The substituent maybe, for example, halogen, such as chloro, bromo or fluoro; nitro;hydroxyl; cyano; carboxyl; or groups which may be further substituted,such as alkyl, including straight or branched chain or cyclic alkyl,such as methyl, trifluoromethyl, ethyl, t-butyl,3-(2,4-di-t-pentylphenoxy) propyl, and tetradecyl; alkenyl, such asethylene, 2-butene; alkoxy, such as methoxy, ethoxy, propoxy, butoxy,2-methoxyethoxy, sec-butoxy, hexyloxy, 2-ethylhexyloxy, tetradecyloxy,2-(2,4-di-t-pentylphenoxy)ethoxy, and 2-dodecyloxyethoxy; aryl such asphenyl, 4-t-butylphenyl, 2,4,6-trimethylphenyl, naphthyl; aryloxy, suchas phenoxy, 2-methylphenoxy, alpha- or beta-naphthyloxy, and 4-tolyloxy;carbonamido, such as acetamido, benzamido, butyramido, tetradecanamido,alpha-(2,4-di-t-pentyl-phenoxy)acetamido,alpha-(2,4-di-t-pentylphenoxy)butyramido,alpha-(3-pentadecylphenoxy)-hexanamido,alpha-(4-hydroxy-3-t-butylphenoxy)-tetradecanamido,2-oxo-pyrrolidin-1-yl, 2-oxo-5-tetradecylpyrrolin-1-yl,N-methyltetradecanamido, N-succinimido, N-phthalimido,2,5-dioxo-1-oxazolidinyl, 3-dodecyl-2,5-dioxo-1-imidazolyl, andN-acetyl-N-dodecylamino, ethoxycarbonylamino, phenoxycarbonylamino,benzyloxycarbonylamino, hexadecyloxycarbonylamino,2,4-di-t-butylphenoxycarbonylamino, phenylcarbonylamino,2,5-(di-t-pentylphenyl)carbonylamino, p-dodecyl-phenylcarbonylamino,p-tolylcarbonylamino, N-methylureido, N,N-dimethylureido,N-methyl-N-dodecylureido, N-hexadecylureido, N,N-dioctadecylureido,N,N-dioctyl-N′-ethylureido, N-phenylureido, N,N-diphenylureido,N-phenyl-N-p-tolylureido, N-(m-hexadecylphenyl)ureido,N,N-(2,5-di-t-pentylphenyl)-N′-ethylureido, and t-butylcarbonamido;sulfonamido, such as methylsulfonamido, benzenesulfonamido,p-tolylsulfonamido, p-dodecylbenzenesulfonamido,N-methyltetradecylsulfonamido, N,N-dipropyl-sulfamoylamino, andhexadecylsulfonamido; sulfamoyl, such as N-methylsulfamoyl,N-ethylsulfamoyl, N,N-dipropylsulfamoyl, N-hexadecylsulfamoyl,N,N-dimethylsulfamoyl, N-[3-(dodecyloxy)propyl]sulfamoyl,N-[4-(2,4-di-t-pentylphenoxy)butyl]sulfamoyl,N-methyl-N-tetradecylsulfamoyl, and N-dodecylsulfamoyl; carbamoyl, suchas N-methylcarbamoyl, N,N-dibutylcarbamoyl, N-octadecylcarbamoyl,N-[4-(2,4-di-t-pentylphenoxy)butyl]carbamoyl,N-methyl-N-tetradecylcarbamoyl, and N,N-dioctylcarbamoyl; acyl, such asacetyl, (2,4-di-t-amylphenoxy)acetyl, phenoxycarbonyl,p-dodecyloxyphenoxycarbonyl methoxycarbonyl, butoxycarbonyl,tetradecyloxycarbonyl, ethoxycarbonyl, benzyloxycarbonyl,3-pentadecyloxycarbonyl, and dodecyloxycarbonyl; sulfonyl, such asmethoxysulfonyl, octyloxysulfonyl, tetradecyloxysulfonyl,2-ethylhexyloxysulfonyl, phenoxysulfonyl,2,4-di-t-pentylphenoxysulfonyl, methylsulfonyl, octylsulfonyl,2-ethylhexylsulfonyl, dodecylsulfonyl, hexadecylsulfonyl,phenylsulfonyl, 4-nonylphenylsulfonyl, and p-tolylsulfonyl; sulfonyloxy,such as dodecylsulfonyloxy, and hexadecylsulfonyloxy; sulfinyl, such asmethylsulfinyl, octylsulfinyl, 2-ethylhexylsulfinyl, dodecylsulfinyl,hexadecylsulfinyl, phenylsulfinyl, 4-nonylphenylsulfinyl, andp-tolylsulfinyl; thio, such as ethylthio, octylthio, benzylthio,tetradecylthio, 2-(2,4-di-t-pentylphenoxy)ethylthio, phenylthio,2-butoxy-5-t-octylphenylthio, and p-tolylthio; acyloxy, such asacetyloxy, benzoyloxy, octadecanoyloxy, p-dodecylamidobenzoyloxy,N-phenylcarbamoyloxy, N-ethylcarbamoyloxy, and cyclohexylcarbonyloxy;amine, such as phenylanilino, 2-chloroanilino, diethylamine,dodecylamine; imino, such as 1 (N-phenylimido)ethyl, N-succinimido or3-benzylhydantoinyl; phosphate, such as dimethylphosphate andethylbutylphosphate; phosphite, such as diethyl and dihexylphosphite; aheterocyclic group, a heterocyclic oxy group or a heterocyclic thiogroup, each of which may be substituted and which contain a 3 to 7membered heterocyclic ring composed of carbon atoms and at least onehetero atom selected from the group consisting of oxygen, nitrogen,sulfur, phosphorous, or boron such as 2-furyl, 2-thienyl,2-benzimidazolyloxy or 2-benzothiazolyl; quaternary ammonium, such astriethylammonium; quaternary phosphonium, such as triphenylphosphonium;and silyloxy, such as trimethylsilyloxy.

If desired, the substituents may themselves be further substituted oneor more times with the described substituent groups. The particularsubstituents used may be selected by those skilled in the art to attainthe desired desirable properties for a specific application and caninclude, for example, electron-withdrawing groups, electron-donatinggroups, and steric groups. When a molecule may have two or moresubstituents, the substituents may be joined together to form a ringsuch as a fused ring unless otherwise provided. Generally, the abovegroups and substituents thereof may include those having up to 48 carbonatoms, typically 1 to 36 carbon atoms and usually less than 24 carbonatoms, but greater numbers are possible depending on the particularsubstituents selected.

The entire contents of the patents and other publications referred to inthis specification are incorporated herein by reference.

EXAMPLES

Sample 1 (Invention, YD-1)

The invention is exemplified in scheme 1 to prepare compound, YD-1:

Preparation of the propargyl alcohol, PA-1: Under a nitrogen atmosphere,4-t-butylphenylacetylene (39.6 g, 250 mMole), was dissolved indimethylformamide (DMF) (400 mL), stirred with a mechanical stirrer andthe solution cool to −10° C. to 0° C. Powdered potassium t-butoxide(KBu^(t)O) (34 g of 95%, 300 mMole), was added over a 10-minute periodand the mixture stirred well for approximately 15 minutes at −10° C. to0° C. To this mixture was then added 4, 4′-di-tert-butylbenzophenone(70.1 g, 238 mMole) all at once. Stirring was continued at −10° C. to 0°C. for approximately 1 hour and then allowed to come to room temperatureover a 1-hour period. At the end of this time the solution was cooled to0° C. and the reaction treated with saturated sodium chloride (100 mL),keeping the temperature below 10° C. The mixture was then diluted withethyl acetate, washed with 2N—HCl (3×100 mL), dried over MgSO₄, filteredand concentrated under reduced pressure. While some solvent was stillpresent, the semi-solid was triturated (500 mL) to give the product asan off-white solid. Yield of propagyl alcohol PA-1, 82 g.

Preparation of Naphthacene Compound, YD-1: Propargyl alcohol PA-1, (40g, 88 mMole) was dissolved in toluene (300 mL), with slight heating toget complete dissolution, cooled and stirred at 0° C. under a nitrogenatmosphere. To this solution was added triethylamine (NEt₃), (12.52 g,16.05 mL, 123 mMole) and then treated drop-by-drop with methanesulfonylchloride (CH₃SO₂Cl), (15.8 g, 110.68 mL 123 mMole), keeping thetemperature of the reaction below 10° C. After the addition, thesolution was stirred at 0° C. for 15 minutes and then at roomtemperature for 15 minutes. To the reaction mixture was then addedfinely powered anhydrous K₂CO₃ (24.3 g, 176 mMole) and then heated, withgood stirring, to 110° C. for 4 hours. After this period, the reactionwas cooled, diluted with ethyl acetate (100 mL) and carefully washedwith 2N—HCl until acidic. The ethyl acetate solution was dried overMgSO₄, filtered and concentrated to give an oil. This oil was dissolvedin ether (100 mL) and slowly treated with methanol (100 mL). On standingthe naphthacene compound, YD-1 crystallized out, was filtered off andwashed with a small volume of methanol and dried. Yield, YD-1, 14 g.

Sample 2 (Inventive, YD-2)

The invention is further exemplified in the following scheme to preparecompound, YD-2:

Preparation of the propargyl alcohol, PA-2: Under a nitrogen atmosphere,4-biphenylacetylene (32.76 g of 97%, 178.31 mMole), was dissolved indimethylformamide (DMF) (750 mL), stirred with a mechanical stirrer andthe solution cool to −10° C. to 0° C. Powdered potassium t-butoxide(KBu^(t)O) (25 g of 95%, 213.97 mMole), was added over a 10-minuteperiod and the mixture stirred well for approximately 15 minutes at −10°C. to 0° C. To this mixture was then added4,4′-di-tert-butylbenzophenone (50 g, 169.81 mMole) all at once.Stirring was continued at −10° C. to 0° C. for approximately 1 hour andthen allowed to come to room temperature over a 1-hour period. At theend of this time the solution was cooled to 0° C. and the reactiontreated with saturated sodium chloride (100 mL), keeping the temperaturebelow 10° C. The mixture was then diluted with ethyl acetate, washedwith 2N—HCl (3×100 mL), dried over MgSO₄, treated with decolorizingcharcoal (×2), filtered and concentrated under reduced pressure. Thecrude product was triturated with ether (200 mL) and heptane (500 mL) togive the product as an off-white solid. Yield of propagyl alcohol PA-2,72 g.

Preparation of Naphthacene Compound, YD-2: Propargyl alcohol PA-2, (5.0g, 10 mMole) was dissolved in toluene (70 mL), with slight heating toget complete dissolution, cooled and stirred at 0° C. under a nitrogenatmosphere. To this solution was added triethylamine (NEt₃), (1.41 g,1.81 mL, 14 mMole) and then treated drop-by-drop with methanesulfonylchloride (CH₃SO₂Cl), (1.79 g, 1.21 mL 14 mMole), keeping the temperatureof the reaction below 10° C. After the addition, the solution wasstirred at 0° C. for 15 minutes and then at room temperature for 15minutes. To the reaction mixture was then added finely powered anhydrousNa₂CO₃ (2.11 g, 20 mMole) and then heated, with good stirring, to 110°C. for 4 hours. After this period, the reaction was cooled, diluted withethyl acetate (100 mL) and carefully washed with 2N—HCl until acidic. Onstanding, the product crystallized out. It was filtered off, washed wellwith methanol and dried. Yield, YD-2, 6.0 g.

Sample 3 (Inventive, YD-3)

Sample 3 is the naphthacene compound YD-3 of the invention. It isprepared from a symmetrical 1,1-diarylpropargyl alcohol in a similarmanner to YD-1 and YD-2.

Sample 4 (Inventive, YD-4)

Sample 4 is the naphthacene compound YD-4 of the invention. It too isprepared from a symmetrical 1,1-diarylpropargyl alcohol in a similarmanner to YD-1 and YD-2

Sample 5 (Comparison, Comp-1)

Sample 5 is a comparison employing naphthacene Comp-1. It is Example 4as described in U.S. Pat. No. 4,855,520 and is prepared from anunsymmetrical 1,1-diarylpropargyl alcohol and produces 3 naphthaceneisomers, Comp-1a, Comp-1b and Comp-1c.

Sample 6 (Comparison, Comp-2)

Sample 3 is another comparison employing naphthacene Comp-2. It isExample 5 as described in U.S. Pat. No. 4,855,520 and is prepared froman unsymmetrical 1,1-diarylpropargyl alcohol and produces 3 naphthaceneisomers, Comp-2a, Comp-2b and Comp-2c.

Sample 7 (Comparison, Comp-3)

Sample 7 is a further comparison employing Comp-3. It is an example notspecifically described in U.S. Pat. No. 4,855,520, but falls within thescope of U.S. Pat. No. 4,855,520. It is prepared from an unsymmetrical1,1-diarylpropargyl alcohol and produces 3 naphthacene isomers, Comp-3a,Comp-3b and Comp-3c.

TABLE 1

Naphthacene Number Sample No. Sample Type Compound(s) formed of Isomers1 Inventive YD-1 1 2 Inventive YD-2 1 3 Inventive YD-3 1 4 InventiveYD-4 1 5 Comparative Comp-1a 3 Comp-1b Comp-1c 6 Comparative Comp-2a 3Comp-2b Comp-2c 7 Comparative Comp-3a 3 Comp-3b Comp-3c

The number(s) of isomeric naphthacene compounds formed in Samples 1-7from the different 1,1-diarylpropargyl alcohols were determined byHPLC/MS analysis.

As can be seen from Table 1, the naphthacenes of the invention YD-1through YD-4 of Samples 1-4 all show the formation of a single isomerwhen a symmetrically substituted 1,1-diarylpropargyl alcohol as in step(a) of the invention is employed. Whereas, the comparison naphthacenesof U.S. Pat. No. 4,855,520, YD-5-YD-7 of Samples 5-7 each show theformation of three isomeric naphthacenes; Comp-1a through Comp-1c,Comp-2a through Comp-2c and Comp-3a through Comp-3c. Since thenaphthacenes of the invention are single isomers they require noseparation before use in EL devices whereas, the comparison naphthaceneseach form three isomers and require separation into their componentsbefore they can be used in EL devices. Symmetrical 1,1-diarylpropargylalcohols used in step (a) of the current invention unexpectedly give asingle naphthacene isomer useful in EL devices to give superiorperformance.

Embodiments of the invention provide a short, simple, environmentallyfriendly procedure, without the formation of mixtures of isomers, andcan be applied to naphthacenes with a variety of substituents. Such highpurity naphthacenes are useful in high performing EL devices.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

The patents and other publications referred to are incorporated hereinin their entirety.

1. A process for synthesizing a naphthacene compound comprising thesteps of: (a) reacting a propargyl alcohol compound with a reagentcapable of forming a leaving group to form a reaction mixture containingan intermediate; and then (b) heating the intermediate in the presenceof a solvent, an inorganic base, and in the absence of any oxidizingagent, to form the naphthacene compound.
 2. A process of claim 1 whereinan acid scavenger is present in step (a).
 3. A process of claim 2wherein said acid scavenger is an amine.
 4. A process of claim 2 whereinsaid acid scavenger is triethylamme.
 5. A process of claim 2 whereinsaid acid scavenger is an inorganic base.
 6. A process of claim 1wherein said inorganic base of step (b) is the basic salt of a metal. 7.A process of claim 1 wherein said inorganic base of step (b) is thebasic salt of a metal from groups 1 and 2 of the periodic table.
 8. Aprocess of claim 1 wherein said inorganic base of step (b) is a metal ornon-metal carbonate.
 9. A process of claim 1 wherein said inorganic baseof step (b) comprises one selected from Li₂CO₃, Na₂CO₃, K₂CO₃, Rb₂CO₃,Cs₂CO₃, MgCO₃, CaCO₃, BaCO₃, sodium acetate(NaOAc), and (NH₄)₂CO₃.
 10. Aprocess of claim 1 wherein steps (a) and (b) employ solvents that aredifferent.
 11. A process of claim 10 wherein the solvent in step (a) isselected from diethyl ether, methylene chloride, ethyl acetate andtetrahydrofuran.
 12. A process of claim 10 wherein the solvent in step(b) is selected from benzene, toluene, xylene and xylene mixtures.
 13. Aprocess of claim 1 wherein steps (a) and (b) employ solvents that arethe same.
 14. A process of claim 13 wherein the solvent is the same forboth steps (a) and (b) and is selected from benzene, toluene andxylenes.
 15. A process of claim 1 wherein the reaction temperature instep (a) is in the range from −30° C. to +30° C.
 16. A process of claim15 wherein the reaction temperature in step (a) is in the range from 0°C. to +20° C.
 17. A process of claim 1 wherein the reaction temperaturein step (b) is in the range from +30°C. to +180° C.
 18. A process ofclaim 17 wherein the reaction temperature in step (b) is in the rangefrom +70° C. to +120° C.
 19. A process of claim 1 wherein the reagentcapable of forming the leaving group comprises one selected from thionylchloride, thionyl bromide, phosphorous pentachloride, phosphoroustrichloride, phosphorous tribromide, phosphorous oxychioride, acetylchloride, and alkanesulfonyl chlorides.
 20. A process of claim 1 whereinthe reagent capable of forming the leaving group comprises one fromthionyl chloride, phosphorous trichloride, and methanesulfonyl chloride.21. A process of claim 1 wherein said intermediate of step (a) isrepresented by Formula (Ia):

wherein: R is hydrogen or a substituent group; R^(a) and R^(b) aresubstituent groups; n is selected from 0-4; m is selected from 0-5; andX is a leaving group.
 22. A process of claim 1 wherein said intermediateof step (a) is represented by Formula (Ib):

wherein: R is hydrogen or a substituent; R^(a) and R^(b) are substituentgroups; n is selected from 0-4; m is selected from 0-5; and X is aleaving group.
 23. A process of claim 1 wherein said intermediate ofstep (a) is represented by Formula (IIa):

wherein: R^(a) and R^(b) are substituent groups; n is selected from 0-4;m is selected from 0-5; and X is a leaving group.
 24. A process of claim1 wherein said intermediate of step (a) is represented by Formula (IIb):

wherein: R^(a) and R^(b) are substituent groups; n is selected from 0-4;m is selected from 0-5; and X is a leaving group.
 25. A process of claim1 wherein said naphthacene compound is represented by Formula (IIIa):

wherein: R is hydrogen or a substituent; R^(a) and R^(b) are substituentgroups; n is selected from 0-4; and m is selected from 0-5.
 26. Aprocess of claim 1 wherein said naphthacene compound is represented byFormula (IlIb):

wherein: R^(a) and R^(b) are substituent groups; n is selected from 0-4;and m is selected from 0-5.
 27. A process of claim 1 wherein saidpropargyl alcohol compound is represented by Formula (IVa):

wherein: R is hydrogen or a substituent; R^(a) and R^(b) are substituentgroups; n is selected from 0-4; and m is selected from 0-5.
 28. Aprocess of claim 1 wherein said propargyl alcohol compound isrepresented by Formula (IVb):

wherein: R^(a) and R^(b) are substituent groups; n is selected from 0-4;and m is selected from 0-5.
 29. A process of claim 21 wherein X isselected from Cl, Br, acetate(OAc), alkanesulfonate, and phosphate. 30.A process of claim 22 wherein X is selected from Cl, Br, acetate(OAc),alkanesulfonate, and phosphate.
 31. A process of claim 21 wherein X isselected from Cl and methanesulfonate(CH₃SO₃).
 32. A process of claim 22wherein X is selected from Cl and methanesulfonate(CH₃SO₃).
 33. Aprocess of claim 25 wherein R comprises one from alkyl, carbocyclic andheterocyclic groups.
 34. A process of claim 26 wherein n and m areindividually at least one, and R^(a) and R^(b) are individually selectedfrom hydrogen, cyano, nitro, halogen, hydroxy, alkyl, alkenyl, alkoxy,aryl, aryloxy, acyl, oxysulfonyl, acyloxy, oxycarbonyl, carboxy,sulfoxide, thio, sulfamoyl, sulfonamido, sulfonyl, carbamoyl,carbonamido, ureido, and trifluoromethyl groups.
 35. A process of claim26 wherein R^(a) and R^(b) individually can form a carbocyclic orheterocyclic ring.
 36. A process of claim 26 wherein R^(a) and R^(b)individually can form an aryl ring.
 37. A process of claim 26 whereinR^(a) and R^(b) individually can form a furyl, imidazolyl, pyrazolyl,pyridyl, pyrrolyl, thienyl, or triazolyl ring.
 38. A process as in claim26 wherein an acid scavenger is present in step (a).
 39. A process ofclaim 26 wherein said acid scavenger is an amine.
 40. A process of claim26 wherein said inorganic base is the basic salt of a metal.
 41. Aprocess of claim 26 wherein said inorganic base is the basic salt of ametal from groups 1 and 2 of the periodic table.
 42. A process of claim26 wherein said inorganic base is a metal or non-metal carbonate.
 43. Aprocess of claim 26 wherein the solvents in steps (a) and (b) aredifferent.
 44. A process of claim 26 wherein the solvents in steps (a)and (b) are the same.
 45. A process of claim 26 wherein the temperaturein step (a) is in the range from −30° C. to +30° C.
 46. A process ofclaim 26 wherein the temperature in step (b) is in the range from +30°C. to +180° C.
 47. A process of claim 26 wherein the reagent capable offorming the leaving group comprises one selected from thionyl chloride,thionyl bromide, phosphorous pentachloride, phosphorous trichloride,phosphorous tribromide, phosphorous oxychloride, acetyl chloride, andalkanesulfonyl chlorides.
 48. A process of claim 23 wherein X isselected from Cl, Br, acetate(OAc), alkanesulfonate(CH₃SO₃), andphosphate.
 49. A process of claim 24 wherein X is selected from Cl, Br,acetate(OAc), alkanesulfonate(CH₃SO₃), and phosphate.
 50. A process ofclaim 1 wherein step (b) is subjected to an inert atmosphere.
 51. Aprocess of claim 26 wherein step (b) is subjected to an inertatmosphere.
 52. A process of claim 1 wherein the reaction time of step(a) is from 5 minutes to 3 hours.
 53. A process of claim 1 wherein thereaction time of step (a) is from 10 minutes to 30 minutes.
 54. Aprocess of claim 1 wherein the reaction mixture of step (b) is heatedfrom 1 to 48 hours.
 55. A process of claim 1 wherein the reactionmixture of step (b) is heated from 1 to 8 hours.
 56. A process of claim1 wherein the reaction mixture of step (b) is heated from 4 to 5 hours.